Both the: i. reflector portion of a headlight (e.g., front light) or a fog light of an automobile; and ii. the interference film reflector for medical uses (surgical light, dental mirror), are mainly formed by using aluminum, nickel, or nickel-chromium as the reflecting material and by forming an interference film by means of dichroic deposition on a reflector base material made of an injection molding body or compression molding body formed using glass, aluminum or other metals, and polyphenyl sulfide, unsaturated polyester resin, polyether imide, or other resins.
That is, a halogen bulb, xenon bulb, high luminance LED or other bulb are used as a light source for the reflector of a headlight (front light) or a fog light of automobile and the interference film reflector for medical uses (surgical light, dental mirror). Since the connection part of such light bulb may be heated to a temperature of 200° C. or higher, it uses an injection molding body or compression molding body of plastic with heat resistance that is improved by blending in metal that has no thermal deformation or glass fiber, calcium carbonate, or other inorganic reinforcer.
However, when glass is used as the reflector base material, it is heavy and easy to break. When metal and reinforcing resin molding body is used as the reflector base material, the weight is large. In addition, in order to improve the reflecting mirror performance (smoothness), it is necessary to perform resin coating or other secondary processing prior to depositing the reflecting material. As a result, the number of the manufacturing steps will be increased.
When a reinforced resin molding body is used as the reflector base material, the weight is relatively small compared with the case of using metal as the reflector base material. However, from the point of view of the strength of the base material and due to limitation of the molding technology, it is necessary to form the reflector base material in a fairly large thickness. As a result, the heat dissipating property of the base material becomes poor. For a projector type lamp having a structure in which heat is easy to accumulate, the heat resistance is unstable, which is undesired for retaining the shape. Also, heating in the housing will be accelerated, shortening the service life of the light bulb itself.
In addition, when a reinforced resin molding body is used as the reflector base material, gas of chlorine compound, etc. may be generated during heating when the lamp is turned on. Said gas will be condensed on the front lens or reflection surface of the headlight to form fog, which will lower the illuminance of the light.
On the other hand, a sheet type reflector made of a film sheet subjected to mirror surface processing by depositing aluminum (for example) is known. Said sheet type reflector has such an advantage that it needs no degreasing or other pretreatment for obtaining the mirror surface property. However, since the film sheet used in this case is made of polyethylene that has poor heat resistance, said sheet type reflector cannot be used as the reflector of the headlight using halogen bulb or other high heating lamp as far as the heat-resistant shape retaining property is concerned.
Also known is a reflecting mirror having a visible light reflecting an IR ray transmitting multi-layer film formed on a reflector base material made of polyimide resin and polyester ketone (for example, see patent reference 2). Such reflecting mirror is difficult to damage and has high resistance against heating of halogen bulb, etc. since the polyimide resin is used. However, since such reflecting mirror has a visible light reflecting IR ray transmitting multi-layer film formed on the base material, it cannot be used as the reflector for a headlight or fog light for automobile in practical application. Also, the characteristic of “having high resistance against the heating of halogen bulb, etc. since polyimide resin is used as the reflector base material” means long molding time since it is necessary to take long time to heat or cool off the die during molding. Therefore, it is unsuitable for practical application as far as cost and mass production are concerned. Besides, when a thermoplastic film with low glass transition point is used, the heat resistance is poor.